One method known in the art for producing organosilicon compounds comprises reacting a silicon hydride containing compound with an unsaturated compound in the presence of a catalyst. This reaction is commonly referred to as hydrosilylation. Typically the catalyst is platinum metal on a support, a platinum compound generally used in an inert solvent, or a platinum complex, however other catalysts comprising rhodium or nickel may be used. In U.S. Pat. No. 2,823,218 to Speier, et al. a method for the production of organosilicon compounds by reacting an Si--H with a compound containing aliphatic carbon atoms linked by multiple bonds in the presence of a chloroplatinic acid is taught. U.S. Pat. No. 3,220,972 to Lamoreaux teaches a similar process however the catalyst is a reaction product of chloroplatinic acid. In EP Patent Application No. 0337197 to Lewis the catalyst used is a rhodium colloid and the silicon containing reactant must have two to three hydrogen atoms bonded to the silicon.
One of the major problems known in the art with hydrosilylations is the de-activation of the catalyst prior to the completion of the reaction. One method for reactivation of the catalyst has been to expose the reaction mixture to oxygen. For example, U.S. Pat. No. 4,578,497 to Onopchenko, et al. teaches the use of an oxygenated platinum containing catalyst for hydrosilylation with alkylsilanes, R'R.sub.x SiH.sub.3-x. The oxygenated platinum catalyst is produced by contacting the catalyst with an oxygen-containing gas. In particular, the catalyst is contacted with the oxygen-containing gas by bubbling air into the catalyst mixed with the olefin and with or without an inert solvent under ambient temperatures prior to the reaction. Another technique taught by Onopchenko is to run the hydrosilylation until de-activation occurs, cool to room temperature and then bubble an oxygen-containing gas into the mixture. Following the exposure to oxygen the system is placed under an inert atmosphere and the reaction is again commenced.
The use of peroxides to activate reactions that are otherwise unreactive in the presence of a metallic catalysts has been shown for several reactants and catalysts. In these situations there is no catalytic activity in the absence of the peroxide. Thus, the peroxide is introduced to "start" or activate the reaction rather than to maintain catalytic activity. For example, Licchelli et al., "Catalyzed Hydrosilylation of 2-Methyl-1-buten-3-yne with Methyldichlorosilane; Promotional Effect Imparted by the Presence of a Different Chlorosilane", Tetrahedron Letters, Vol.28,No. 2, pp.3719-3722 (1987) discloses the reaction between 2-methyl-1-butene-3-yne and methyldichlorosilane using chloroplatinic acid and a very small amount of benzoyl-peroxide. In the absence of the peroxide the reaction did not take place.
Dickers et al., "Organosilicon Chemistry. Part 24. Homogeneous Rhodium-catalyzed Hydrosilation of Alkenes and Alkynes: Role of Oxygen or Hydroperoxides", J.C.S. Dalton, pp. 308-313 (1980) discloses the reaction between purified hex-1-ene or hex-yne and triethylsilane in the presence of a rhodium catalyst, [RhCl(PPh.sub.3).sub.3 ], and Bu.sup.t OOH. In the absence of Bu.sup.t OOH the reaction did not take place. Additionally, Di-t-butyl peroxide did not activate the reaction.
Calhoun et al., "Organic Peroxide Assisted Transition Metal Hydrosilylation Catalysis", Transition Met. Chem., 8, 365-368(1983), discloses peroxides as co-catalysts to increase the catalytic activity of rhodium catalysts. For example Calhoun shows that the yield of the reaction between 1-octene and triethoxysilane was only 4% in the absence of t-BuOOH but increased to 75% when high amount of t-BuOOH was added to the reaction mixture.
It is an object of this invention to provide a method for maintaining catalytic activity during a hydrosilylation reaction wherein the hydrosilylation reaction comprises reacting a silicon hydride having 1 to 3 hydrogen atoms attached to the silicon with unsaturated compounds in the presence of a platinum catalyst and a peroxide.